Investigation on the transferability of algorithms for the numerical optimization of cooling channel design in injection molding on metal gravity die casting

Abstract

The thermal mold design and the identification of a proper cooling channel design are primordial steps in the development of complex molds for injection molding. In order to find a suitable cooling channel system, a lot of effort is needed to avoid part warpage after solidification. In current research, a simulative procedure to optimize the cooling channel layout iteratively is being developed at the Institute of Plastics Processing. These algorithms are transferred to the metal gravity die casting process, which has several similar requirements to the mold. Effectively, the simulation is simplified to a heat conduction problem. Instead of water, high temperature resistant oil is deployed and the casted material is a A356 aluminum alloy instead of semi-crystalline plastics. The algorithm is adapted to these changed boundary conditions and the calculation of the optimized heat distribution is performed. Aim of this procedure is the construction of a mold producing parts with less warpage than a conventional mold. Keywords: Thermal mold design / inverse heat conduction / cooling channel layout / heat transfer / metal gravity die casting Die thermische Werkzeugauslegung und die Identifizierung eines geeigneten Kühlkanaldesigns sind grundlegende Schritte in der Konstruktion komplexer Werkzeuge für das Spritzgießen von Kunststoffen. Um ein passendes Kühlkanaldesign zu finden, das den Bauteilverzug während der Erstarrung minimiert, muss großer Aufwand betrieben werden. Aus diesem Grund wird eine simulative Prozesskette am Institut für Kunststoffverarbeitung der RWTH Aachen entwickelt, die das Kühlkanallayout des Spritzgießwerkzeuges iterativ optimiert. Diese Algorithmen werden auf den Prozess des Metalldauerformgusses übertragen, der ähnliche Anforderungen an den Formenbau hat. Die Methodik wird an diese veränderten Randbedingungen angepasst und die Berechnung der optimierten Wärmeverteilung in der Form erfolgt. Ziel dieser Optimierung ist die Konstruktion einer Gussform zur Produktion von Bauteilen mit verringertem Verzug im Vergleich zu einer konventionell gefertigten Form.

Development of an Experimental Setup to Investigate Influences on Component Distortion in Gravity Die Casting and a First Variation of Temperature Control Strategy

“…The accompanying simulations showed that cooling channels adapted to the heat distribution in the component can somewhat reduce the occurrence of thermal extremes in the component and mold. This is much less pronounced when considering the modules that can be used in reality, as could be seen in the first purely numerical considerations of idealized cooling channel layouts [7]. The small extent of the expected differences makes a comparison of the measured in-situ values (here the temperature) with the calculated ones poorly possible.…”

“…It can be seen that the edges of the "U" are the hottest part in the mold and that in the casting the areas far away of the inlet are the coldest. Furthermore, during tool design in cooperation with the Institute of Plastics Processing (IKV) at RWTH Aachen University, the transferability of a developed algorithm for plastic injection molding for the optimization of the cooling channel layout for a more homogeneous solidification was considered [7]. This was done to test the transferability of the hypothesis that a homogeneously solidifying component produces less distortion, which was found to be true in plastic injection molding, to metal casting.…”

“…This approach, originally developed for plastics in injection molding, was transferred to metal casting in a numerical framework and its applicability was evaluated. A recognizable potential became apparent as well as limitations in transferability, which are to be expected due to strongly differing thermophysical material properties between plastics and metals [7].…”

Evaluating the Application of Heating Conductor Surfaces Inside Plasma Sprayed Coatings in Permanent Mold Metal Casting Processes for Local, Near-Surface Heat Release

“…This in general represents a method with a highly inert reaction time with recent research focusing on optimizing the cooling channel design to improve heat dissipation at hotspot locations. 10 This study evaluates the potentials and possibilities of the application of heating conductor layers inside plasma sprayed coatings for permanent mold gravity die casting of an aluminum alloy. The specifications of a TiO 2 /Cr 2 O 3 heating conductor coating system described by Bobzin et al 11 are used in order to estimate the thermal surface power densities such a coating can realistically provide.…”